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Question : The quality department at an electronics component


The quality department at an electronics component manufacturer must ensure that their components will operate at prespecified levels. The accompanying table shows a frequency distribution with measured resistance values (in ohms) for a sample of 520 resistors. The sample mean and the sample standard deviation are 4,790 ohms and 40 ohms, respectively.

Resistance ……………………………………………………………………………………. Frequency
Under 4,740 ……………………………………………………………………………………………... 44
4,740 up to 4,780 ……………………………………………………………………………………… 145
4,780 up to 4,820 ……………………………………………………………………………………… 197
4,820 up to 4,860 ……………………………………………………………………………………… 107
4,860 or more ……………………………………………………………………………………………... 27
Total = 520

a. Using the goodness-of-fit test for normality, state the competing hypotheses to test if the sample data suggest that resistance does not follow the normal distribution.
b. At α = 0.05, what is the conclusion to the test?
c. Would your conclusion change at the 10% significance level?